evermore.c

gpsd, a popular GPS daemon.

/* $Id: evermore.c 4661 2008-01-19 22:54:23Z garyemiller $ */
/*
 * This is the gpsd driver for EverMore GPSes operating in binary mode.
 * About the only thing this gives us that NMEA won't is TDOP.
 * But we'll get atomic position reports from it, which is good.
 *
 * The vendor site is <http://www.emt.com.tw>.
 *
 * This driver was written by Petr Slansky based on a framework by Eric S. 
 * Raymond.  The following remarks are by Petr Slansky.
 *
 * Snooping on the serial the communication between a Windows program and
 * an Evermore chipset reveals some messages not described in the vendor
 * documentation (Issue C of Aug 2002):
 *
 * 10 02 06 84 00 00 00 84 10 03	switch to binary mode (84 00 00 00)
 * 10 02 06 84 01 00 00 85 10 03	switch to NMEA mode (84 01 00 00)
 *
 * 10 02 06 89 01 00 00 8a 10 03        set baud rate 4800
 * 10 02 06 89 01 01 00 8b 10 03        set baud rate 9600
 * 10 02 06 89 01 02 00 8c 10 03        set baud rate 19200
 * 10 02 06 89 01 03 00 8d 10 03        set baud rate 38400
 *
 * 10 02 06 8D 00 01 00 8E 10 03        switch to datum ID 001 (WGS-84)
 * 10 02 06 8D 00 D8 00 65 10 03        switch to datum ID 217 (WGS-72)
 *
 * These don't entail a reset of GPS as the 0x80 message does.
 * 
 * 10 02 04 38 85 bd 10 03     answer from GPS to 0x85 message; ACK message
 * 10 02 04 38 8d c5 10 03     answer from GPS to 0x8d message; ACK message
 * 10 02 04 38 8e c6 10 03     answer from GPS to 0x8e message; ACK message
 * 10 02 04 38 8f c7 10 03     answer from GPS to 0x8f message; ACK message
 *
 * The chip sometimes sends vendor extension messages with the prefix
 * $PEMT,100. After restart, it sends a $PEMT,100 message describing the
 * chip's configuration. Here is a sample:
 *
 * $PEMT,100,05.42g,100303,180,05,1,20,15,08,0,0,2,1*5A
 * 100 - message type
 * 05.42g - firmware version
 * 100303 - date of firmware release DDMMYY
 * 180 -  datum ID; 001 is WGS-84
 * 05 - default elevation mask; see message 0x86
 * 1 - default DOP select (1 is auto DOP mask); see message 0x87
 * 20 - default GDOP; see message 0x87
 * 15 - default PDOP
 * 08 - default HDOP
 * 0 - Normal mode, without 1PPS
 * 0 - default position pinning control (0 disable, 1 enable)
 * 2 - altitude hold mode (0 disable, 1 always, 2 auto)
 * 1 - 2/1 satellite nav mode (0,1,2,3,4)
 *          0 disable 2/1 sat nav mode
 *          1 hold direction (2 sat)
 *          2 clock hold only (2 sat)
 *          3 direction hold then clock hold (1 sat)
 *          4 clock hold then direction hold (1 sat)
 * 
 * Message $PEMT,100 could be forced with message 0x85 (restart):
 * 10 02 12 85 00 00 00 00 00 01 01 00 00 00 00 00 00 00 00 87 10 03
 * 0x85 ID, Restart
 * 0x00 restart mode (0 default, 1 hot, 2 warm, 3 cold, 4 test)
 * 0x00 test start search PRN (1-32)
 * 0x00 UTC second (0-59)
 * 0x00 UTC Minute (0-59)
 * 0x00 UTC Hour (0-23)
 * 0x01 UTC Day (1-31)
 * 0x01 UTC Month (1-12)
 * 0x0000 UTC year (1980+x, uint16)
 * 0x0000 Latitude WGS-84 (+/-900, 1/10 degree, + for N, int16)
 * 0x0000 Longtitude WGS-84 (+/-1800, 1/10 degree, + for E, int16)
 * 0x0000 Altitude WGS-84 (-1000..+18000, meters, int16)
 * 0x87 CRC
 * 
 * With message 0x8e it is possible to define how often each NMEA
 * message is sent (0-255 seconds). It is possible with message 0x8e
 * to activate PEMT,101 messages that have information about time,
 * position, velocity and HDOP.
 * 
 * $PEMT,101,1,02,00.0,300906190446,5002.5062,N,01427.6166,E,00259,000,0000*27
 * $PEMT,101,2,06,02.1,300906185730,5002.7546,N,01426.9524,E,00323,020,0011*26
 * 101 - message type, Compact Navigation Solution
 * 2 - position status (1,2,3,4,5,6)
 *      (1 invalid, 2 2D fix, 3 3D fix, 4 2D with DIFF, 5 3D with DIFF,
 *       6 2/1 sat degrade mode) 
 * 06 - number of used satelites
 * 02.1 - DOP (00.0 no fix, HDOP 2D fix, PDOP 3D fix)
 * 300906185730 - date and time, UTC ddmmyyHHMMSS (30/09/2006 18:57:30)
 * 5002.7546,N - Latitude (degree)
 * 01426.9524,E - Longitude (degree)
 * 00323 - Altitude (323 metres)
 * 020 - heading (20 degrees from true north)
 * 0011 - speed over ground (11 metres per second); documentation says km per h
 * 
 * This is an exampe of an 0x8e message that activates all NMEA sentences 
 * with 1s period:
 * 10 02 12 8E 7F 01 01 01 01 01 01 01 01 00 00 00 00 00 00 15 10 03
 * 
 * There is a way to probe for this chipset. When binary message 0x81 is sent:
 * 10 02 04 81 13 94 10 03
 *
 * EverMore will reply with message like this:
 * *10 *02 *0D *20 E1 00 00 *00 0A 00 1E 00 32 00 5B *10 *03
 * bytes marked with * are fixed
 * Message in reply is information about logging configuration of GPS
 *
 * Another way to detect the EverMore chipset is to send one of the messages 
 * 0x85, 0x8d, 0x8e or 0x8f and check for a reply.
 * The reply message from an EverMore GPS will look like this:
 * *10 *02 *04 *38 8d c5 *10 *03
 * 8d indicates that message 0x8d was sent;
 * c5 is EverMore checksum, other bytes are fixed
 *
 */

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <ctype.h>
#include <unistd.h>
#include <time.h>
#include <stdio.h>

#include "gpsd_config.h"
#include "gpsd.h"
#if defined(EVERMORE_ENABLE) && defined(BINARY_ENABLE)

#define LITTLE_ENDIAN_PROTOCOL
#define GET_ORIGIN 1
#define PUT_ORIGIN 0
#include "bits.h"

#define EVERMORE_CHANNELS	12

/*@ +charint -usedef -compdef @*/
static bool evermore_write(struct gps_device_t *session, unsigned char *msg, size_t msglen)
{
   unsigned int       crc;
   size_t    i, len;
   unsigned char stuffed[MAX_PACKET_LENGTH*2], *cp;

   /* prepare a DLE-stuffed copy of the message */
   cp = stuffed;
   *cp++ = 0x10;  /* message starts with DLE STX */
   *cp++ = 0x02;

   len = (size_t)(msglen + 2);   /* msglen < 254 !! */
   *cp++ = (unsigned char)len;   /* message length */
   if (len == 0x10) *cp++ = 0x10;
   
   /* payload */
   crc = 0;
   for (i = 0; i < msglen; i++) {
       *cp++ = msg[i];
       if (msg[i] == 0x10) *cp++ = 0x10;
       crc += msg[i];
   }

   crc &= 0xff;

   /* enter CRC after payload */
   *cp++ = crc;  
   if (crc == 0x10) *cp++ = 0x10;

   *cp++ = 0x10;   /* message ends with DLE ETX */
   *cp++ = 0x03;

   len = (size_t)(cp - stuffed);

   /* we may need to dump the message */
   gpsd_report(LOG_IO, "writing EverMore control type 0x%02x: %s\n", msg[0], 
	       gpsd_hexdump(stuffed, len));
#ifdef ALLOW_RECONFIGURE
   return (gpsd_write(session, stuffed, len) == (ssize_t)len);
#else
   return 0;
#endif /* ALLOW_RECONFIGURE */
}
/*@ -charint +usedef +compdef @*/

/*@ +charint @*/
gps_mask_t evermore_parse(struct gps_device_t *session, unsigned char *buf, size_t len)
{
    unsigned char buf2[MAX_PACKET_LENGTH], *cp, *tp;
    size_t i, datalen;
    unsigned int used, visible, satcnt;
    double version;
    gps_mask_t mask = 0;

    if (len == 0)
	return 0;

    /* time to unstuff it and discard the header and footer */
    cp = buf + 2;
    tp = buf2;
    if (*cp == 0x10) cp++;
    datalen = (size_t)*cp++;
   
    gpsd_report(LOG_RAW, "raw EverMore packet type 0x%02x, length %d: %s\n", *cp, len, gpsd_hexdump(buf, len));

    datalen -= 2;

    for (i = 0; i < (size_t)datalen; i++) {
	*tp = *cp++;
	if (*tp == 0x10) cp++;
	tp++;
    }

    /*@ -usedef -compdef @*/
    gpsd_report(LOG_RAW, "EverMore packet type 0x%02x, length %d: %s\n", buf2[0], datalen, gpsd_hexdump(buf2, datalen));
    /*@ +usedef +compdef @*/

    (void)snprintf(session->gpsdata.tag, sizeof(session->gpsdata.tag),
		   "EID%d",(int)buf2[0]);

    switch (getub(buf2, 1))
    {
    case 0x02:	/* Navigation Data Output */
	session->gpsdata.fix.time = session->gpsdata.sentence_time
	    = gpstime_to_unix((int)getuw(buf2, 2), getul(buf2, 4)*0.01) - session->context->leap_seconds;
	ecef_to_wgs84fix(&session->gpsdata, 
			 getsl(buf2, 8)*1.0, getsl(buf2, 12)*1.0, getsl(buf2, 16)*1.0,
			 getsw(buf2, 20)/10.0, getsw(buf2, 22)/10.0, getsw(buf2, 24)/10.0);
	used = getub(buf2, 26) & 0x0f;
	visible = (getub(buf2, 26) & 0xf0) >> 4;
	version = getuw(buf2, 27)/100.0;
	/* that's all the information in this packet */
	if (used < 3)
	    session->gpsdata.fix.mode = MODE_NO_FIX;
	else if (used == 3)
	    session->gpsdata.fix.mode = MODE_2D;
	else {
	    session->gpsdata.fix.mode = MODE_3D;
	    mask |= ALTITUDE_SET | CLIMB_SET;
	}
	gpsd_report(LOG_PROG, "NDO 0x02: version %3.2f, mode=%d, status=%d, visible=%d, used=%d\n",
		    version,
		    session->gpsdata.fix.mode,
		    session->gpsdata.status,
		    visible,
		    used);
	mask |= TIME_SET | LATLON_SET | TRACK_SET | SPEED_SET | MODE_SET | CYCLE_START_SET;
	if (session->subtype[0] == '\0') {
	    (void)snprintf(session->subtype, sizeof(session->subtype), 
		       "%3.2f", version);
	    mask |= DEVICEID_SET;
	}
	return mask;

    case 0x04:	/* DOP Data Output */
	session->gpsdata.fix.time = session->gpsdata.sentence_time
	    = gpstime_to_unix((int)getuw(buf2, 2), getul(buf2, 4)*0.01) - session->context->leap_seconds;
	session->gpsdata.gdop = (double)getub(buf2, 8)*0.1;
	session->gpsdata.pdop = (double)getub(buf2, 9)*0.1;